Altered responsiveness to basic sensory input is an under-studied symptom in autism spectrum disorders (ASD) that likely has far-reaching effects on development, although these effects are not well understood. While the term sensory typically connotes stimuli external to the body, there is copious sensory information within the body as well, including visceral and proprioceptive signals. Hypo-responsiveness to external sensory stimuli shows very strong association with core clinical symptoms, and differentiates ASD from other developmental disorders better than hyper-responsiveness. The experiments described in this project are designed to investigate possible mechanisms for this under-responsiveness, and attempts to reconcile these with growing evidence that individuals with ASD show enhanced reliance on internal sensory signals when they are in competition with external cues. We predict that basic sensory perception of internal (interoceptive) and external sensory cues will not differ in ASD, but expect differences in higher order neural networks that integrate these signals and compare competing signals for salience in order to allocate attention. The project will emphasize the salience network, comprising anterior insular and anterior cingulate cortices, which integrate both internal and external cues with limbic input to determine their relative affective significance. We hypothesize that this system is involved in excessive focus on internal sensory cues, at the expense of external input, in ASD. We further predict that the neural and behavioral correlates of enhanced attention to internal sensory input relative to external will positively relate to social deficits and sensory hypo-responsiveness in ASD. If these predictions are supported, neural differences in the salience network could serve as novel biomarkers for ASD and behavioral differences could be parlayed into improved therapeutic approaches, including mindfulness-based therapies that could capitalize on an existing strength in attending to internal sensory cues.